What the barracuda do at 9 a.m.

The Sipadan permit system limits the boats. There are mornings when South Point belongs to two crews and the barracuda belong to themselves. We rolled in at 0852, descended to twenty-two metres, and held the wall.

At 0856 the school was already there. They are usually there. What is interesting is what they do — the way the formation tightens and loosens with the tide, how the body of the school moves laterally along the wall while its individual fish swim against the current. From below, the school looks stationary. The fish themselves are working hard.

At 0907 the formation rotated. Not the slow drift one might imagine: a sudden, near-vertical spiral that took maybe forty seconds to complete and then held, mid-water, like a fixed object. We stayed at twenty-two and watched. Two of the divers in our group ran out of memory cards. One did not bother trying — there is a kind of dive that is for the eye, not the lens.

At 0918 the formation broke. The fish dispersed along the wall in groups of fifty or so, and within a minute there was no school. Just the wall and the deep blue and a pair of trevally going the other way. Twenty-two minutes, end to end. The boat was waiting. We surfaced quietly, without saying much.